In late October we flew into Naples, took the airport bus to the ferry terminal and took the fast ferry to Procida for 2 nights. It's a lovely little island, smaller than both Ischia and Capri. You can walk the whole thing in a day. If you stayed a third night you could easily do a day trip to Ischia and/or Capri. When we traveled it was the week after the seasonal ferries ended but I think in season there is a ferry to Sorrento or maybe somewhere else on the AC. (Double check schedules, I could be wrong). In our case we took a ferry back to Naples, the bus to the central train station and a train to Salerno where we based ourselves for 4 nights. We did day trips to Amalfi town, Pompeii and Paestum. Salerno has a lot to offer and is a good base for day trips, but if you're really interested in spending time on the AC you might prefer to stay in one of the towns. In late October the regularly scheduled ferry was cancelled every day we were there which only left the bus (very crowded) and train to Vietri sul Mare. While we loved our time in Salerno and really enjoyed Pompeii and even more so Paestum, our day spent in Amalfi town was slightly underwhelming. Very crowded, we didn't have plan except to walk around so we actually kept walking through the main street and found a little path up a hill overlooking homes and lemon trees. Next time I will stay in one of the towns on the AC and look to walk some of the paths between the towns.
For this trip we didn't stay in Naples (after Salerno we went to Puglia for a week) but we've enjoyed Naples a few other times. Lots to see and do, and great food! Just be ready for a gritty urban feel, but that's part of it's charm.